Par stability determinant

The par stability determinant is a 400 bp locus of the pAD1 plasmid which encodes a type I toxin-antitoxin system in Enterococcus faecalis.^[1][2] It was the first such plasmid addiction module to be found in gram-positive bacteria.^[3]

FstAT
Secondary structure of FstAT
Identifiers
Symbol	fstAT
Rfam	RF01797
Other data
RNA type	Gene; antitoxin
Domain(s)	Enterococcus faecalis
PDB structures	PDBe

Fst Type I toxin-antitoxin system
Identifiers
Symbol	Fst_toxin
Pfam	PF13955
TCDB	1.C.64
OPM superfamily	225
OPM protein	2kv5
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

The par locus contains two genes: fst which encodes a 33-amino acid toxic protein and a gene for RNAII, the small RNA anti-toxin which inhibits fst translation.^[4] The two genes are found on opposite DNA strands and share a 5' region which is where they are thought to have an antisense interaction.^[4] Their RNA secondary structures have been predicted computationally, the complementary regions appear to be presented on exposed loops for interaction.^[4]

par maintains pAD1 by means of post-segregational killing (PSK). If a daughter cell does not inherit the par locus, the unstable RNAII will quickly degrade leaving the long-lived fst toxin to damage or kill the daughter cell.^[5]

See also

• Hok/sok system